In polishing of wafers, especially conventional mechanical polishing methods which are required not to cause defects, such as mechanical strain, in the wafer while keeping a desired polishing speed, it is possible to keep such polishing speed by using larger abrasive grains and/or a higher polishing load. However, because of various defects caused by polishing, it has been impossible to ensure the compatibility between keeping a desired polishing speed and no defect. Thus there was proposed a polishing method of CMP (Chemical-Mechanical Planarization). This method permits the above compatibility by a combination of mechanical and chemical polishing actions. The CMP method is widely used in the finish polishing process of silicon wafers, which requires the compatibility between keeping a desired polishing speed and no defect in the wafers. With the increasing packing density of devices in recent years, it has become necessary, in a specific manufacturing stage of integrated circuits, to polish a wafer or the surface of a semiconductor substrate in which conductive and dielectric layers are formed on the surface of a wafer. Semiconductor substrates are polished to remove surface defects such as high protuberances and roughness. Usually, this process is performed during forming various devices and integrated circuits on the wafer. This polishing process requires the compatibility between keeping a desired polishing speed and no defect like as the finish polishing process on silicon wafers. In this polishing process for the integrated circuits, the above Chemical-Mechanical Planarization (CMP) is performed by introducing chemical slurry, which gives a higher polishing removal speed and no defect characteristic to the surface of a semiconductor. In general, the CMP process includes a step which involves holding a thin and flat semiconductor material under a controlled condition of pressure and temperature on a wet abrasive surface, and rotating the semiconductor material.
In one example of the CMP process, a polishing pad is used, which comprises polyurethane resin or the like, and a chemical slurry of around pH 9 to 12, the chemical slurry being a suspension consisting of an alkaline solution, e.g. caustic soda, ammonia, amine or the like, and silica particles. Polishing is performed by bringing a semiconductor substrate into relatively rotational contact with the polishing pad while supplying a flow of the chemical slurry onto the polishing pad. When conditioning the polishing pad, closed substances and foreign substances are removed by conditioning with utilization of an abrasive tool on which diamond grains are supported by an electrodeposited layer, conditioning while supplying a flow of water or the chemical slurry onto the polishing pad.
The conditioner used in the CMP process is essentially different from conventional cutting or grinding tools in the following points. In cutting tools, even if a small number of hard abrasive grains are lost therefrom due to release, the cutting capacity is not deteriorated in the case where other hard abrasive grains remain on the fresh surface of the tools after release of the abrasive grains. In contrast, regarding the CMP conditioner, since abrasive grains released therefrom damage the surface of the semiconductor substrate, the abrasive grains are not allowed to release from the conditioner even if the number thereof is small. Further, since the CMP conditioner is used at a low rotational speed in a wet process, it does not require such heat resistance and extreme wear resistance as required to the cutting tools. With regard to conventional tools which have a problem of release of abrasive grains, there is a cutting tool in which abrasive grains, each consisting of a comparatively coarse single grain (generally, an order of not less than 1 mm of diameter), are bonded to a metallic support material. However, the conventional cutting tools are essentially different from the conditioner used in the CMP process in the following points. In contrast to the conventional cutting tools which use coarse abrasive grains, each consisting of a comparatively coarse single grain, as stated above, with regard to the conditioner used in the CMP process, abrasive grains each having a comparatively small size (50 to 300 .mu.m of diameter) are bonded to a base member of the conditioner so as to form a single surface layer. Further, since the CMP conditioner is used at a low rotational speed in a wet process, it does not require such heat resistance and extreme wear resistance as required to the cutting tools.
Conventionally, polishing pads have been conditioned by means of an abrasive tool on which diamond grains are supported by an electrodeposited nickel. Electrodeposition with nickel has been widely used because it can be relatively easily applied to metallic support materials. However, bonding strength between the electrodeposited nickel and diamond grains is not sufficient and releasing and breaking down of diamond grains often occurred so as to damage polishing pads and semiconductor substrates. Thus, a conditioner free from release of diamond grains have been sought.
In the case of the CMP polishing for producing a Shallow Trench Isolation (STI) structure or for an insulating film to be positioned between layers, for example, which poses a problem of decrease in the polishing speed especially due to clogging in the polishing pad, so-called the "in situ conditioning", which is carried out during polishing, is effective in comparison with a case where polishing and conditioning are separately performed. On the other hand, however, occurrence of scratches due to release of diamond grains has become more remarkable in the "in situ conditioning", thus it has been desired to establish a new "in situ dressing" method utilizing a conditioner without release of diamond grains.